Switching rate in the presence and absence of tryptophan.

A. Temporal change in the ratio of the number of induced to suppressed cells in the presence of tryptophan with 300 µM (filled circles) and 400 µM (open circles) TMG. The solid (300 µM) and broken (400 µM) lines are the fitting curves according to the population dynamics model (Materials and Methods). Gray lines represent the exponential fit when considering the lag time. The switching rates were calculated as 0.014 (solid line in black), 0.070 (broken line in black), 0.017 (solid line in gray) and 0.085 h−1cell−1 (broken line in gray), respectively. Error bars show the standard deviations. B. Cumulative distribution of the wait time of the first induced cell born from the initial population of 1,000 or 100 suppressed cells, in the absence of tryptophan with 300 (solid line) or 400 µM (broken line) TMG, respectively. The average wait times were 8.6 h for 300 µM TMG and 2.7 h for 400 µM TMG. C. Switching rates in the presence (filled bars) and absence (open bars) of tryptophan. The switching rate was determined as the inverse of wait time divided by the number of cells in the initial population; e.g., 0.00012 h−1cell−1 = 1/8.6/1,000.